Panic exit devices of the type to which the invention relates commonly incorporate a push plate or bar spanning the width of the doorway which is pushed to unlatch and swing the door open. The devices translate the inward (and outward) movement of the push bar to throw the door latch.
By their name, the devices are typically used on doors of emergency exits, such as emergency escape doors, or doors which are used to allow the passage of large crowds, such as in a gymnasium. The dependable and quick operation of these devices is obviously crucial.
Panic exit devices using a push plate are shown in Folger, U.S. Pat. No. 4,083,590, and Zawadzki, U.S. Pat. No. 3,730,574, for example. Such devices often resorted to complicated mechanisms to provide for the orthogonal (or rectilinear) movement of the push bar no matter where the bar might be pushed, in order to assure release of the latch. Moreover, because these devices were of more complex construction, they were generally subject to greater maintenance.
It is accordingly desirable that the panic exit device operate consistently, that it be durable, and as non-complex as possible to assure consistent and durable operation.
In panic exit devices, it is also advantageous to provide for the device to be dogged, i.e., secured, in the unlatched position. This is especially important when the door is subjected to substantial traffic, such as a door in a gymnasium, arena and the like, where the door may need to be kept open or unlatched for long periods of time. Zawadzki, U.S. Pat. No. 3,730,574, shows a dogging mechanism for a panic exit device.
It is desirable, however, to prevent the panic exit device from becoming unintentionally dogged, particularly when latched. If this occurred, it then may become impossible to unlatch the door without first undogging the door. Obviously, a door in such a condition could present a serious safety problem.